ROCK OUTCROPS Rocks that are exposed at the Earth’s surface are called outcrops. The physical setting of outcrops vary depending on a number of factors including rock type, structure, landscape processes, climate and human activity. In New Mexico outcrops occur in all mountain ranges, along stretches of rivers, canyons and arroyos and along roadways and highways. The dry climate of New Mexico enhances outcrop exposure by inhibiting vegetation growth. Highway and roadway outcrops are especially attractive to geologists since they offer exposures of rock that have not been subjected to significant weathering. In other regions of the United States outcrops occur as sea cliffs (Northwest Pacific and coast of Maine), low ledges in recently glaciated areas (New England) and exposures of poorly lithified sedimentary rocks (Southeastern US Coastal Plains). In regions of scarce outcrop (Great Plains and Coastal Plains), soil covers much of the outcrops and geologists have to be satisfied with the rare river bank or highway outcrop.